We propose to investigate whether there is correlation between differential staining properties of human chromosomes (Chromosome heteromorphisms) from different individuals and the patterns of in situ hybridization with various satellite DNAs. Satellites II, III, IV, B, C, D, Hoechst fraction 1 and 340bpEco R, will be isolated from pooled placental tissue by Ag-CsSO4 and Hoechst-CsC1 centrifugation. Radioactive probes will be prepared by nick translation of each of the purified repetitious DNA components in the presence of highly radioactive (3H) deoxynucleoside triphosphates. Metaphase chromosome preparations from 30 individuals with striking heteromorphisms as revealed by staining with quinacrine mustard, C-banding, Giesma-11 banding and G-banding will be denatured with HCL. In situ hybridization will be performed with each of the radioactive probes on the chromosome spreads. Grain counts of the autoradiographs of the hybridized chromosomes will be done to determine whether the location and/or the degree of hybridization of any of the DNA probes corresponds to the location and/or degree of staining with the Q-band, C-band, Giesm-11 or G-banding techniques.